Currently, electric energy required in vehicles is supplied by the generator in the vehicle, and the generator is driven by the engine to generate and supply power. For supplying a backup power, a rechargeable battery is configured in the vehicle, which is charged by the generator.
However, inventors finds out the following drawbacks during study, first, the conventional engine management system and the conventional generator couldn't adjust the power-generation voltage, thus the generated energy is wasted and the fuel consumption is increased, furthermore, the rechargeable battery is deeply discharged to lower the lifetime of the battery, thereby the primary energy recovery of the generator can't be achieved.